Vessel for laying a pipeline and comprising an a &amp; r means

ABSTRACT

A vessel ( 1 ) for laying a pipeline, the vessel comprising a hull structure ( 3 ) comprising one or more floaters ( 4 ), a tower ( 5 ) defining a firing line ( 6 ) when positioned in a pipelaying position, the tower ( 5 ) being pivotable relative to the hull structure ( 3 ) about a tower pivot axis ( 7 ), and an A &amp; R means ( 8 ) for abandoning and/or recovering the pipeline, wherein the tower ( 5 ) is pivotable about said tower pivot axis ( 7 ) substantially independent from the A &amp; R means ( 8 ) and the A &amp; R means ( 8 ) is configured to operate while the tower ( 5 ) is pivoted about said tower pivot axis ( 7 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage of International Application No.PCT/NL2007/000327, filed Dec. 21, 2007, the contents of which isincorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to a vessel for laying a pipeline, the vesselcomprising a hull structure comprising one or more floaters, a towerdefining a firing line when positioned in a pipelaying position, thetower being pivotable relative to the hull structure about a tower pivotaxis, and an A&R means for abandoning and/or recovering the pipeline.The firing line is the line along which the pipeline is lowered to aseabed. The tower positioned in the pipelaying position defines thefiring line. During pipelaying, the pipeline leaves the tower along thefiring line.

BACKGROUND OF THE INVENTION

Such a vessel is known from the prior art. During the laying of thepipeline the tower is positioned in an upright position, with an anglerelative to the hull structure that is variable. If for one reason oranother, the pipelaying operation has to be stopped, for instance whenbad weather conditions are forecasted, the vessel has to be prepared forpipe abandonment. This means that the pipeline has to be abandoned fromthe vessel by positioning the pipeline on the seabed. Furthermore, thetower has to be pivotally lowered towards the hull structure and placedin a lowered position. The pipeline may remain connected to the vesselvia for example a cable. Because of the high waves which occur duringbad weather, the length of said cable must be such that it providessufficient clearance between the vessel and the pipeline.

The known vessel abandons the pipeline by means of the A&R means whichare provided in the tower. Said A&R means generally comprises reelingmeans with long cables. During the abandoning operation it is requiredthat the tower remains in an upright position. After the pipeline ispositioned on the seabed, the lowering of the tower towards the hullstructure and in the lowered position can be started. Said preparationof the vessel for bad weather is a time consuming operation. This isalso the case for the preparation of the vessel for resuming anoperation, for instance after the weather conditions have improved. Forthis, the tower has first to be raised from the hull structure to anupright position. After that, the pipeline can be recovered by the A&Rmeans.

This means that the preparation of the vessel for bad weather or forresuming an operation after bad weather is very time consuming. Due tothis, costly operational time in which pipeline can be laid is lost.

Furthermore, due to the fact that the preparation of the vessel for badweather is very time consuming, said preparation has to be started longbefore the bad weather is expected to arrive. The accuracy of a weatherforecast highly depends on the time period in which said forecast ismade. This means that a bad weather forecast which is made several hoursbefore the actual arriving of the bad weather is far more accurate thana forecast made one day or more before the arrival of said bad weather.With the known vessel it often happens that due to the a wrong weatherforecast, the vessel is taken out of operation and prepared for badweather, while said bad weather at the end changes of course and doesnot arrive at the vessel location. Many hours of operational time oftenlost this way.

SUMMARY OF THE INVENTION

An object of the invention is to provide a vessel which allows a fasterpreparation of the vessel for bad weather or for operation after badweather.

The object is achieved by that the tower is pivotable about said towerpivot axis substantially independent from the A&R means and the A&Rmeans is configured to operate while the tower is pivoted about saidtower pivot axis.

This has the following effects. For the preparation of the vessel forbad weather, the lowering of the tower does not have to wait until thepipeline is abandoned. For the preparation of the vessel for operationafter bad weather, the recovering of the pipeline does not have to waituntil the tower is raised in an upright position relative to the hullstructure. Costly operational time is saved this way.

Furthermore, it will be clear that by reducing the required time toprepare the vessel for bad weather it is possible to make the decisionfor such a preparation on basis of a more accurate weather forecast.This means that the risk that the vessel is taken out of operation andprepared for bad weather while said bad weather does not arrive at thevessel is reduced.

In an embodiment of the vessel according the invention, the A&R meanscomprises a static construction substantially fixed in a specificposition. The A&R means are positioned in a position suitable forabandoning or recovering the pipeline, while the tower is pivoted.

In a further embodiment of the vessel according the invention, the A&Rmeans is movable relative to the hull structure and substantiallyindependent of the tower. The A&R means may be pivotable relative to thehull structure about an A&R pivot axis and substantially independent ofthe tower. The A&R pivot axis may extend substantially parallel with thetower pivot axis. The tower pivot axis and the A&R pivot axis may extendsubstantial perpendicular to the firing line of the tower. The A&R pivotaxis may substantially coincide with the tower pivot axis. The pivotalmovement of the tower may define a pivot plane and the A&R means may bepivotable in said pivot plane. Each of these configurations provides apractical and/or constructional advantage.

In another embodiment of the vessel according the invention, the A&Rmeans is configured such that the A&R means is movable between aposition in the firing line and a position outside the firing line. Whenpositioned in the firing line, the A&R means may advantageously be usedfor abandoning and/or recovering the pipeline. When positioned outsidethe firing line, the A&R means allow the passage of a large structure(like an inline structure) along the firing line. Additionally, whenpositioned outside the firing line the A&R means may be used in adifferent function than A&R of a pipeline.

In an embodiment of the vessel according the invention, the vesselcomprises a hang off means for hanging off the pipeline, wherein thetower is pivotable independent of the hang off means. The hang off meansmay for example comprise a hang off table, one or more friction clampsor one or more tensioners. The hang off means may be movable relative tothe hull structure and substantially independent of the tower. The hangoff means may be pivotable relative to the hull structure about a hangoff pivot axis and substantially independent of the tower. The hang offpivot axis may extend substantially parallel with the tower pivot axis.The hang off pivot axis may extend substantially perpendicular to thefiring line of the tower. The hang off pivot axis may substantiallycoincide with the tower pivot axis. The pivotal movement of the towermay define a pivot plane and the hang off means may be pivotable in saidpivot plane. Each of these configurations provides a practical and/orconstructional advantage.

In a further embodiment of the vessel according the invention, the hangoff means is configured such that the hang off means is movable betweena position in the firing line and a position outside the firing line.When positioned in the firing line, the hang off means may advantageousbe used for hanging off the pipeline. When positioned outside the firingline, the hang off means allow the passage of a large structure (like anin-line-structure) along the firing line.

In another embodiment of the vessel according the invention, the vesselcomprises a line up means for lining up the pipeline, wherein the lineup means is movable substantially independent of the tower. The line upmeans may be configured such that the line up means is movable between aposition in the firing line and a position outside the firing line. Whenpositioned in the firing line, the line up means may advantageous beused for lining up the pipeline along the firing line. When positionedoutside the firing line, the line up means allow the passage of a largestructure (like an inline structure) along the firing line. The line upmeans may be pivotable about a line up pivot axis. The line up means maybe pivotable connected to the A&R means.

In an embodiment of the vessel according the invention, the A&R meanscomprises an U-shaped frame which is at two ends thereof pivotableconnected to the vessel. The tower may comprise a U-shaped base which isat two ends thereof pivotable connected to the vessel and wherein theU-shaped frame of the A&R means in may be located inside the U-shapedbase of the tower.

In a further embodiment of the vessel according the invention, thevessel comprises a workstation, which is movable between a position inwhich the work station is located in the firing line to a secondposition in which the work station is positioned outside the firingline.

The invention also relates to a method of laying a pipeline with avessel comprising a hull structure comprising one or more floaters, atower defining a firing line when positioned in a pipelaying position,an A&R means for abandoning and recovering the pipeline, which methodcomprises the abandoning and/or recovering of the pipeline by means ofthe A&R means while pivotally moving the tower about a tower pivot axisand relative to the hull structure. The method may comprise the step inwhich the tower is pivotally lowered to the hull structure while thepipeline is abandoned and/or the step in which the tower is pivotallyraised from the hull structure while the pipeline is recovered.

The invention further relates to a method of laying a pipeline with avessel according to the invention, comprising the steps of positioningthe A&R means in a hoisting position,—hoisting an item with the A&Rmeans, and moving the A&R means such that the hoisted item is positionedin the firing line.

The A&R means may be located outside the firing line when the item ispositioned in the firing line. The hang off means may be located outsidethe firing line when the item is positioned in the firing line. The lineup means may be located outside the firing line when the item ispositioned in the firing line. This is advantageous when the item is alarge structure (like an inline structure).

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in details with reference to theaccompanying drawings wherein:

FIG. 1A schematically shows a side view of an embodiment of the vesselaccording the invention during pipelaying;

FIG. 1B schematically shows an enlarged view of part I of FIG. 1A duringpipelaying;

FIG. 2 schematically shows a view in cross section along the line II-IIof FIG. 1;

FIG. 3 shows an enlarged view of part III of FIG. 2;

FIG. 4 schematically shows the vessel of FIG. 1 during the abandoning ofthe pipeline;

FIG. 5 shows an enlarged view of part V of FIG. 1 during the passage ofan inline structure and

FIG. 6 shows an enlarged view of part VI of FIG. 1 during the hoistingof an item from the deck of the hull structure by the A&R means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1A and/or 1B show an embodiment of a vessel according theinvention, the water line 30 and the sea bed 31. The vessel 1 is usedfor the laying of a pipeline 2. The vessel 1 comprises a hull structure3 with two floaters 4, and a deck 34 positioned on top of those floaters4. A tower 5 is positioned at the bow of vessel 1. The tower 5 ispositioned in a pipelaying position 11 in which it defines a firing line6 along which the pipeline 2 is laid. During pipelaying, the pipeline 2is constructed from pipe sections and leaves the tower 5 along thefiring line 6. The pipelaying position 11 of the tower 5 is determinedby the pipe departure angle. The tower 5 is pivotable connected to thevessel 1 such that the tower 5 can pivot relative to the hull structure3 about a tower pivot axis 7. The pivot movement of the tower 5 isindicated by arrow 41. The tower 5 may be lowered from said pipelayingposition to the deck 34 into a laid down position 29. Said pivotmovement of the tower 5 defines a pivot plane (10 of FIG. 2) in whichthe tower 5 is pivotable.

The vessel 1 furthermore, comprises A&R means 8 which is pivotable aboutan A&R pivot axis 9. The tower 5 is pivotable independently from the A&Rmeans 8. The A&R means is configured to operate while the tower 5 ispivoted about the tower pivot axis 7. Said operation of the A&R meansmay be the abandoning and/or recovery of the pipeline 2. The A&R means 8is pivotable relative to the hull structure 3 and independent of thetower 5. The pivot movement of the A&R means 8 is indicated by arrow 42.The A&R means 8 is positioned behind the firing line 6. The position ofthe A&R means 8 is adjustable by means of an A&R adjuster 32.

The vessel 1 further comprises a hang off means 14 for hanging of thepipeline 2. The tower 5 and the hang off means 14 are pivotableindependently from each other. The hang off means 14 is pivotablerelative to the hull structure 3 about a hang off pivot axis 15. Thehang off means 14 is in this figure positioned in the firing line 6. Thepivotable movement of the hang off means 14 is indicated by arrow 43.

Line up means 18 are connected to the A&R means 8. Said line up means 18are pivotable about a line up pivot axis 21. Said pivot movement isindicated by arrow 45. The line up means 18 serve to line up a pipesection positioned in the tower along the firing line 6. In this figure,the line up means is positioned in the firing line 6.

A workstation 25 is provided for giving shelter to persons working onthe pipeline 2. Said workstation 25 is arranged such that it is movableas by arrow 44. In this figure the workstation 25 is positioned in thefiring line 6. It may be moved along said arrow 44 to a position outsidethe firing line.

Due to the specific configuration of the vessel 1, it is possible toabandon or recover the pipeline 2 with the A&R means while pivotallymoving the tower 5 about the tower pivot axis 7 and relative to the hullstructure 3. Because of this it is possible to pivotally lower the tower5 to the deck 34 while the pipeline 2 is abandoned. It is also possibleto pivotally raise the tower 5 from the deck 34 while the pipeline 2 isrecovered.

FIG. 2 shows a view in cross section of the vessel of FIG. 1. The pivotplane 10 in which the tower 5 is pivotable is indicated. The tower 5comprises an U-shaped base 23. Said U-shaped base 23 is with two ends 24thereof pivotable connected to the vessel 1.

The A&R means 8 comprise an U-shape frame 22 which is with two ends 33thereof pivotable connected to the vessel 1. The U-shaped frame 22 ofthe A&R means 8 is located inside the U-shapes base 23 of the tower 5.The line up means 18 are pivotable connected to the A&R means 8. Thetower pivot axis 7, A&R pivot axis 9 and hang off pivot axis 15coincide.

FIG. 3 shows in an enlarged view part III of FIG. 2. The tower pivotaxis 7, A&R pivot axis 9 and pivot axis 15 are clearly shown is thisfigure. The tower 5, A&R means 8 and hang off means 14 can all pivotindependently from each other. Although in the drawing all three pivotaxes coincide, relatively small height differences may be applied. Ifthe A&R means 8 is pivotable connected to the tower such that the A&Rpivot axis 9 is located at a relatively small distance above the towerpivot axis 7 (seen from the view of FIG. 3), then the A&R means 8 issubstantially movable independent from the tower 5 even though the A&Rmeans 8 may be subjected to a small displacement when the tower 5 ispivoted. The same applies to the hang off means 14 and the line up means18.

FIG. 4 shows an enlarged view of part IV of FIG. 1 during an abandonmentor recovery operation. The tower 5 is shown in the laid down position 29but may be raised to the pipelaying position during the A&R operation.The A&R means 8 is positioned in the firing line 6 such that the A&Rwire 38 can be lowered or raised following the firing line 6. To enablethe A&R operation, the line up means 18 are positioned outside thefiring line 6. Also the hang off means 14 are positioned outside thefiring line 6. During a recovery operation, the hang off means 14 can berotated into the firing line 6 after A&R head 39, which is connected tothe end of pipeline 2, is lifted above said hang off means 14 positionedin the firing line 6.

FIG. 5 shows in an enlarged view part V of FIG. 1 while an inlinestructure 35, is positioned along the firing line 6. The A&R means 8,hang off means 17, workstation 25 and line up means 18 are positionedoutside the firing line 6. Because of this, space is created so that theinline structure 35 can be positioned along the firing line 6 andlowered, for instance with a travelling block (not shown), such thatinline structure 35 passes the A&R means 8, hang off means 14,workstation 25 and line up means 18. After passage of the bulky part ofthe inline structure 35 the collar 46 on the stem 40 of the inlinestructure can be positioned such hang off means 14 can be pivoted in thefiring line 6 and under said collar 46 (shown in dotted lines). Collar46 can then be hung off on said hang off means 14 positioned in thefiring line 6. The workstation 25 can be moved in the firing line 6 andthe line up means 18 can be pivoted into said firing line in order toreceive additional pipe sections. In the situation that a pipeline endtermination (PLET) is used, the A&R means 8 can be pivoted into thefiring line 6 for connection of the A&R cable 38 to the PLET for laydownof the completed pipeline on the seabed 31.

FIG. 6 shows an enlarged view of part VI of FIG. 1 while an item 36 ishoisted from the deck 34. The A&R means 8 is positioned in a hoistingposition 28. In said hoisting position the A&R means 8 is positionedbetween the firing line 6 and the deck 34 of the hull structure 3. Theworkstation 25 is positioned in the firing line 6. The line up means 18are positioned adjacent to the frame of the A&R means 8. This way, theitem 36 can be hoisted by the A&R means 8 and subsequently moved bypivotally moving the A&R means 8. It is possible to pivot the A&R means8 such that the item 36 is positioned in the firing line 6 or in aposition past the firing line 6.

It will be clear to the person skilled in the art that many differentembodiments are possible without departing from the scope of theinvention.

1. A vessel for laying a pipeline, the vessel comprising a hullstructure comprising one or more floaters, a tower defining a firingline when positioned in a pipelaying position, the tower being pivotablerelative to the hull structure about a tower pivot axis, and an A&Rmeans for abandoning and/or recovering the pipeline, wherein the toweris pivotable about said tower pivot axis substantially independent fromthe A&R means and the A&R means is configured to operate while the toweris pivoted about said tower pivot axis.
 2. The vessel according to claim1, wherein the A&R means is movable relative to the hull structure andsubstantially independent of the tower.
 3. The vessel according to claim1, wherein the A&R means is pivotable relative to the hull structureabout an A&R pivot axis and substantially independent of the tower. 4.The vessel according to claim 3, wherein the A&R pivot axis extendssubstantially parallel with the tower pivot axis.
 5. The vesselaccording to claim 3, wherein the tower pivot axis and the A&R pivotaxis extend substantially perpendicular to the firing line of the tower.6. The vessel according to claim 3, wherein the A&R pivot axissubstantially coincides with the tower pivot axis.
 7. The vesselaccording to claim 3, wherein the pivotal movement of the tower definesa pivot plane and the A&R means is pivotable in said pivot plane.
 8. Thevessel according to claim 1, wherein the A&R means is configured suchthat the A&R means is movable between a position in the firing line anda position outside the firing line.
 9. The vessel according to claim 1,wherein the vessel comprises a hang off means for hanging off thepipeline, wherein the tower is pivotable independent of the hang offmeans.
 10. The vessel according to claim 9, wherein the hang off meansis movable relative to the hull structure and substantially independentof the tower.
 11. The vessel according to claim 9, wherein the hang offmeans is pivotable relative to the hull structure about a hang off pivotaxis and substantially independent of the tower.
 12. The vesselaccording to claim 11, wherein the hang off pivot axis extendssubstantially parallel with the tower pivot axis.
 13. The vesselaccording to claim 11, wherein the hang off pivot axis extendssubstantially perpendicular to the firing line of the tower.
 14. Thevessel according to claim 11, wherein the hang off pivot axissubstantially coincides with the tower pivot axis.
 15. The vesselaccording to claim 11, wherein the pivotal movement of the tower definesa pivot plane and the hang off means is pivotable in said pivot plane.16. The vessel according to claim 9, wherein the hang off means isconfigured such that the hang off means is movable between a position inthe firing line and a position outside the firing line.
 17. The vesselaccording to claim 1, wherein the vessel comprises a line up means forlining up the pipeline and said line up means is movable relative to thehull structure and substantially independent of the tower.
 18. Thevessel according to claim 17, wherein the line up means is configuredsuch that the line up means is movable between a position in the firingline and a position outside the firing line.
 19. The vessel according toclaim 17, wherein the line up means is pivotable about a line up pivotaxis.
 20. The vessel according to claim 19, wherein the line up meansare pivotable connected to the A&R means.
 21. The vessel according toclaim 19 wherein the line up means are releasable connected to the hangoff means.
 22. The vessel according to claim 4, wherein the A&R meanscomprises an U-shaped frame which is at two ends thereof pivotableconnected to the vessel.
 23. The vessel according to claim 22, whereinthe tower comprises a U-shaped base which is at two ends thereofpivotable connected to the vessel and wherein the U-shaped frame of theA&R means in located inside the U-shaped base of the tower.
 24. Thevessel according to claim 1, wherein the vessel comprises a workstation,which is movable between a position in which the work station is locatedin the firing line to a second position in which the work station ispositioned outside the firing line.
 25. A method of laying a pipelinewith a vessel comprising a hull structure comprising one or morefloaters, a tower defining a firing line when positioned in a pipelayingposition, an A&R means for abandoning and recovering the pipeline, whichmethod comprises the abandoning and/or recovering of the pipeline bymeans of the A&R means while pivotally moving the tower about a towerpivot axis and relative to the hull structure.
 26. The method Methodaccording to claim 25, wherein the tower is pivotally lowered to thehull structure while the pipeline is abandoned.
 27. The method Methodaccording to claim 25, wherein the tower is pivotally raised from thehull structure while the pipeline is recovered.
 28. A method of laying apipeline with a vessel according to claim 2, comprising positioning theA&R means in a hoisting position, hoisting an item with the A&R means,and moving the A&R means such that the hoisted item is positioned in thefiring line.
 29. The method Method according to claim 28, wherein theA&R means are located outside the firing line when the item ispositioned in the firing line.
 30. The method Method according to claim28, wherein the hang off means are located outside the firing line whenthe item is positioned in the firing line.
 31. A vessel according toclaim 28, wherein the line up means are located outside the firing linewhen the item is positioned in the firing line.
 32. Use of the vessel ofclaim 1.